Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND SYSTEM FOR UPSETTING HOLLOW MEMBERS
FIELD OF THE INVENTION
[0001] The present invention relates to a system and method for
upsetting hollow metal members. More specifically, the present invention
relates
to a system and method for upsetting hollow metal members without requiring
the member to be heated for the upsetting operation.
BACKGROUND OF THE INVENTION
[0002] It is
sometimes required to have a hollow metal member with a
thicker gauge (wall thickness) at a relatively small portion of one end or
both
ends, of the member while the majority of the length of the member between the
ends can be a second, thinner, gauge. For example, rear axles in front wheel
drive passenger vehicles are typically manufactured from a hollow tubular
metal
member which is formed into the required configuration in a press. While the
axle requires a given wall thickness, for example three millimeters, along
most of
its length, the end portions of the axle can require an increased wall
thickness,
for example four and a half millimeters, to allow them to be affixed, by
welding, to
the wheel hub structures.
[0003] Rather
than employ a feedstock member having the greater
wall thickness (e.g. four and a half millimeters) along its entire length,
(which
would increase material costs and the weight of the member) it is known to
employ a feedstock member having the smaller wall thickness (e.g. three
millimeters) and to upset, or bulge, the ends of the feedstock member to
obtain
the necessary larger wall thickness required at the ends of the axle.
[0004]
Conventionally, upsetting involves heating the end portions of
the hollow member to place the material in a malleable state and then
longitudinally compressing the member to deform it, increasing the wall
thickness (gauge) of the hollow member in the treated area while decreasing
its
length.
[0005] While
hot upsetting provides an advantage in that localized
areas of increased gauge can be created, it does suffer from some
disadvantages. In particular, hot upsetting must be performed at a separate
manufacturing station where the ends of the hollow member can be heated and
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compressed and this increases the manufacturing time for the finished part, as
well as the increasing the capital costs associated with providing a separate
upsetting station and increasing the operating costs associated with operating
the heaters for the upsetting operation.
[0006] Further, the heating
required for hot upsetting requires a
heating and cooling cycle for the upset portions of the hollow member and this
heating and cooling cycle alters the properties of the hollow member in the
upset
areas. This typically necessitates that the upset areas be subsequently
treated to
harden the upset areas, adding a further process expense.
[0007] It is desired to have a
method and system for upsetting at least
one end portion of a hollow member which does not require the heating of the
hollow member.
SUMMARY OF THE INVENTION
[0008] It is an object
of. the present invention to provide a novel system
and method for upsetting a portion of a hollow member which obviates or
mitigates at least one disadvantage of the prior art.
[0009] According to a
first aspect of the present invention, there is
provided a method of upsetting a hollow workpiece, comprising the steps of:
loading a workpiece into a clamp, the clamp having a shape complementary to
the outer surface of the workpiece; extending an open end of the workpiece
that
is to be upset outside of the clamp; inserting a mandrel into the interior of
the
workpiece, through a die having a through-passage located adjacent the end of
the workpiece and into the open end of the workpiece, the mandrel having a
complementary shape to the interior cross section of the workpiece and the
mandrel first entering the through-passage of the die from a side opposite of
the
clamp and next entering the workpiece and then entering the clamp, and the
through-passage shaped and sized smaller than an outside shape and size of
the end of the workpiece; closing the clamp; urging the die toward the clamp
to
bring a substantially planar drive face within the cavity of the die into
contact with
an end face the workpiece, without the end of the workpiece entering into the
through-passage; driving the die toward the clamp to decrease the length of
the
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end of the workpiece to be upset while increasing the wall thickness of that
portion; and once the die has been urged a pre-selected distance toward the
clamp, retracting the die from the end, retracting the mandrel from the
workpiece,
and opening the clamp to remove the upset workpiece.
[0010] According to another
aspect of the present invention, there is
provided an apparatus for upsetting a hollow workpiece, comprising: a clamp
for
gripping the workpiece at a location offset from an open end of the workpiece
that is to be upset, the clamp having a clamp surface shaped and sized
complementary to the outer shape and size of the hollow workpiece; a die
having
an inner cavity shaped and sized corresponding to a desired upset shape and
size of the end of the workpiece and having a through-passage in
communication with the cavity, the through-passage shaped and sized smaller
than the outer shape and size of the hollow workpiece; a mandrel having a
shape and size complementary to the interior surface of the workpiece, the
mandrel being moveable into and out of the open end of the workpiece that is
to
be upset, the mandrel being positionable within the clamped portion of the
workpiece, wherein the mandrel is axially moveable from a first position clear
of
the die and the clamp to a second position within the die and the clamp, the
mandrel first entering the through-passage of the die from a side of the die
opposite of the clamp and next entering the hollow interior of the workpiece
and
then entering the clamp; and a drive operable to move the die toward the clamp
such that a substantially planar drive face within the cavity of the die
engages an
end face of the workpiece to be upset without the end of the hollow workpiece
entering into the through-passage, the drive further operable to urge the die
a
pre-selected distance toward the clamp to upset the workpiece including
decreasing the length of the end of the workpiece while increasing the wall
thickness of the workpiece.
[0011] The present
invention provides an apparatus and method for
upsetting a portion of a hollow workpiece to increase the wall thickness of
the
workpiece. A mandrel is inserted into an exposed end of the workpiece and into
a clamp, which is then closed to hold the workpiece. A die is forced against
the
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exposed end of the workpiece to upset the exposed end by compressing the end
towards the clamp, decreasing its length and increasing the wall thickness of
the
hollow member as required.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Preferred embodiments of the present invention will now be
described, by way of example only, with reference to the attached Figures,
wherein:
[0013] Figure 1 shows a schematic representation of an upsetting
apparatus in accordance with the present invention;
[0014] Figure 2 shows the apparatus of Figure 1 with a clamp closed
about a workpiece and with a portion of a mandrel extended into the workpiece
and clamp;
[0015] Figure 3 shows a cross section, taken through line 3-3 of
Figure
2, of a clamp, workpiece and mandrel in accordance with the present invention;
[0016] Figure 4 shows the apparatus of Figure 2 with a die urged
towards the clamp;
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[0017] Figure 5 shows the apparatus of Figure 4 with the die
retracted
from the upset workpiece;
[0018] Figure 6 shows the apparatus of Figure 5 with the mandrel
retracted and the clamp opened to allow removal of the upset workpiece;
[0019] Figure 7a shows a workpiece prior to upsetting;
[0020] Figure 7b shows the workpiece of Figure 7a after upsetting;
[0021] Figure 8a shows a cross section through a clamp, workpiece
and mandrel where the workpiece is square in cross section; and
[0022] Figure 8b shows a cross section through a clamp, workpiece
and mandrel where the workpiece is rectangular in cross section.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Apparatus for performing upsetting, in accordance with the
present invention, is indicated generally at 20 in Figure 1. In Figure 1, a
hollow
workpiece 24 is loaded in an upsetting clamp 28 with the end 32 of hollow
workpiece 24 which is to be upset being inserted into an upsetting die 36. The
interior dimensions of die 36 correspond to the desired finished upset size
for
workpiece 24.
[0024] Once workpiece 24 is loaded in clamp 28 and die 36, a
mandrel
40 is inserted into the interior of workpiece 24, through dies 36, and extends
into
workpiece 24 such that at least a portion of mandrel 40 is within clamp 28, as
shown in Figure 2. The outer dimensions of mandrel 40 closely correspond to
the inner dimensions of workpiece 24.
[0025] Clamp 28 is then closed, as shown in Figure 2, and tightly
engages the outer surface of workpiece 24. Clamp 28 and mandrel 40 prevent
any deformation of the portion of workpiece 24 held within clamp 28 as shown
in
Figure 3.
[0026] In the illustrated embodiment, workpiece 24 has a circular
outer
shape and clamp 28 has a corresponding circular shape of its inner clamp
surface to receive workpiece 24 and mandrel 40 also has an outer circular
shape
and size corresponding to the circular shape of the interior of workpiece 24.
However, as will be apparent to those of skill in the art, the present
invention is
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not limited to upsetting hollow workpieces 24 with circular outer (or inner)
shapes.
[0027] The end 32 of workpiece 24 to be upset extends beyond clamp
28, as shown in Figures 1 and 2, into die 36.
[0028] Once clamp 28 is
closed and mandrel 40 is inserted into
workpiece 24, upsetting die 36 is forced towards clamp 28, as shown in Figure
4,
upsetting end 32 by shortening its length while increasing its gauge.
Specifically,
the length of end 32 is decreased and the material which is displaced by this
decrease in length is added to the wall thickness of end 32, increasing its
gauge.
Mandrel 40 prevents the inner dimensions of end 32 from changing, and the
displaced material therefore increases the wall thickness of end 32 until the
outer
dimensions of end 32 correspond to the inner dimensions of die 36.
[0029] As
will be apparent to those of skill in the art, the force required
to move die 36 towards clamp 28 can be significant. In a presently preferred
embodiment of the invention, die 36 is mounted to one half cam 44 of a cam-
based force multiplier. The other half cam 48 of the cam-based force
multiplier
is connected to a hydraulic ram 52 which, when extended, moves half cam 48
laterally with respect to the length of end 32. As will be understood by those
of
skill in the art, half cam 48 includes a cam surface which rides on a
complementary cam surface on half cam 44, converting the lateral force exerted
on half cam 48 by ram 52 into longitudinal force on half cam 44, and die 32,
and
increasing the longitudinal force applied to die 36, and end 32, from that
generated by ram 52.
[0030]
However, as will be apparent to those of skill in the art, the
present invention is not limited to the use of force multipliers to move die
36 into
contact with end 32 and force can be applied directly to die 36 (or a suitable
carrier) in any appropriate manner as will occur to those of skill in the art.
[0031] When
die 36 has been driven a predetermined distance
towards clamp 28, achieving the desired upsetting, ram 52 is stopped and
reversed. A ram (not shown) or other suitable means moves die 36 away from
clamp 28, exposing upset end 32 as shown in Figure 5.
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[0032] The
clamp pressure on clamp 28 is reduced to allow mandrel
40 to be retracted and then clamp 28 is released, as shown in Figure 6, and
upset workpiece 24 can be removed from apparatus 20.
[0033] A
method in accordance with the present invention can be
considered to comprise the steps of: loading a workpiece into a clamp, the
clamp
having a shape complementary to the outer surface of the workpiece, and the
portion of the workpiece which is to be upset extending outside of the clamp;
inserting a mandrel into the interior of the workpiece through a die located
adjacent end of the workpiece to be upset, the outer surface of the mandrel
having a complementary shape complementary to the interior cross section of
the workpiece and the mandrel extending sufficiently into the workpiece to
enter
the portion of the workpiece to be held in the clamp; closing the clamp;
urging
the die toward the clamp to bring the die into contact with the workpiece;
driving
the die toward the clamp to decrease the length of the end of the workpiece to
be upset while increasing the wall thickness of that end; and once the die has
been force a pre-selected distance towards the clamp, retracting the die and
the
mandrel from the workpiece and opening the clamp to remove the upset
workpiece.
[0034] It
should be appreciated that the orientation of die 36 and
mandrel 40 relative to end 32 of workpiece 24 allows a concurrent upsetting
operation to be performed at the opposite end of workpiece 24. In particular,
it is
contemplated that another die and another mandrel substantially the mirror
images of die 36 and mandrel 40 are positioned at the opposite end of
workpiece
24. The another die and another mandrel are moveable in the same manner as
die 36 and mandrel 40 to upset the opposite end of workpiece 24. Die 36 and
the other die may be simultaneously driven into contact with workpiece 24 to
substantially simultaneously upset both ends of workpiece 24. A singular clamp
28 may be used or another clamp may be added to grasp workpiece 24 near the
end opposite end 32, depending on the length of workpiece 24.
[0035] Figure 7a shows
a workpiece 24 prior to upsetting in apparatus
20. As shown, workpiece 24 has a length of A and includes an end 32 which is
to be upset. Figure 6b shows the workpiece 24 of Figure 6a after upsetting in
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apparatus 20. As shown, the length of workpiece 24 has been reduced by the
upsetting from a length of A to a length of B and the wall gauge of workpiece
24
in end 32 has been increased.
[0036] In a
specific example of the present invention, a workpiece
comprising a circular tube of 22MNB5 steel which has been subjected to an NBK
process (comprising post rolling annealing at approximately 920 C in a
controlled atmosphere and controlled heating and cooling cycles) has an end
upset. The wall thickness of the workpiece is 3.2 mm with the outer diameter
of
the workpiece being 90 mm. After upsetting, the upset portion has a wall
thickness of approximately 4.2 mm, and an outer diameter of about 92 mm, and
the length of the workpiece is reduced by approximately 15 mm.
[0037] In
this example, apparatus 20 forms part of a press station for
forming workpiece 24 and clamp 28 is closed by the same hydraulic press which
is otherwise used to form workpiece 24. Accordingly, clamp 28 is closed with a
force in excess of 250 tonnes. Ram 52, produces in excess of 50 tonnes of
force, which the cam-based force multiplier converts to greater than 150
tonnes
of lateral force on die 36 and end 32.
[0038] As
will be apparent to those of skill in the art, apparatus 20 can
be provided as a separate workstation in a manufacturing process, but as
mentioned above, it is contemplated that one of the advantages of the present
invention is that apparatus 20 can be included in an existing workstation,
such as
a forming press. In this manner, cycle times can be reduced, along with the
capital expenses which would otherwise be required to establish a separate
work
station and/or the need for additional plant floor space.
[0039] Further, as the
method of the present invention does not require
heating of workpiece 24 for upsetting, the capital and operating expenses
which
would be associated with upsetting heaters is avoided and the need for
additional hardening or other processing treatments can be avoided.
[0040] As
mentioned above, while the illustrated embodiment shows
workpiece 24 as having a circular cross section, the present invention is not
so
limited. Figure 8a shows a cross section through a clamp 28a for a workpiece
24a with a square cross section. Clamp 28a includes four moveable clamp
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portions 100, 104, 108 and 112 each of which is urged into contact with a
respective side of workpiece 24a when clamp 28a is closed.
[0041] As
will be apparent to those of skill in the art, in this
embodiment, mandrel 40 has a square cross section corresponding to the
interior cross section of workpiece 24a.
[0042]
Similarly, Figure 8b shows a clamp 28b for a workpiece 24b
with a rectangular cross section. Clamp 28b includes four moveable clamp
portions 116, 120, 124 and 128 each of which is urged into contact with a
respective side of workpiece 24b when clamp 28b is closed. As with the
embodiment of Figure 8a, in this embodiment, mandrel 40 has a square cross
section which is complementary to the interior cross section of workpiece 24b.
In both of these examples, die 36 will have a shape and size which corresponds
to the desired upset end 32, whether that desired upset end 32 is square,
rectangular or any other desired shape.
[0043] It is further
contemplated that die 36 can include one or more
desired features, such as a flat or spline, which is formed into the
corresponding
part of the outer surface of upset portion 30 by dies 36 when the upsetting is
performed.
[0044] The above-described embodiments of the invention are
intended to be examples of the present invention and alterations and
modifications may be effected thereto, by those of skill in the art, without
departing from the scope of the invention which is defined solely by the
claims
appended hereto.
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